Synthesis and Application of AgNPs-Chitosan Composite as a Self-Disinfecting Coating in Water-Based Polyurethane

Infectious diseases still represent an important cause of mortality for humans. One of the main reasons is that various pathogenic bacteria can persist and survive on inanimate surfaces for many days. Therefore, self-disinfection coating technology has become of interest to deal with this problem. In this research, we propose to develop a self-disinfection coating containing AgNPs-chitosan composite in 50% water-based polyurethane (WPU), which has a strong short- and long-term antibacterial effect. The coating agent was synthesized by conventional composite approaches. The physical and chemical properties of AgNPs-chitosan nanocomposite are studied by TEM, SEM, and FTA 100 Drop Shape Instrument B Frame System. The results show that at a concentration of 39 μg/mL, when reducing the size of AgNPs from 7.29 ± 1.65 to 4.66 ± 2.08 nm, the shape of a sphere turns into an asymmetrical circle and leads to increasing aggregation of AgNPs. Negative charges on the surface of AgNPs interact with amine (-NH2) and hydroxyl (-OH) groups of chitosan through an electrostatic force. All formulations of the coating showed low hydrophobicity properties. Moreover, the short- and long-term antibacterial activity of the coating were investigated by application of the ISO 22196 standard protocol. The mean inhibition percentage of E. coli O157:H7 and S. aureus ATCC25722 of the formulation containing AgNPs at a concentration of 1280 µg/mL and 50% v/v of WPU (Formula 4) and the formulation containing AgNPs at a concentration of 1280 µg/mL, chitosan 39 µg/mL and 50% v/v of WPU (Formula 8) from 1 day to 4 months after the coating completely dried was 81.72% ± 3.15% and 82.07% ± 3.01% on E. coli O157:H7, 84.64% ± 2.59% and 83.27% ± 3.12% on S. aureus ATCC25722, respectively. There was no significant difference from statistical analysis at 95% confidence interval (p < 0.05). Furthermore, the quantify of silver ion from coating was measured by ICP-MS. The result reveal that the formulation containing AgNPs at a concentration of 1280 µg/mL, chitosan 39 µg/mL and 50% v/v of WPU (Formula 8) released an amount of silver ion lower than the formulation containing AgNPs at a concentration of 1280 µg/mL and 50% v/v of WPU (Formula 4) by approximately 5.92 times, while the same concentration of AgNPs and inhibition efficacy was not significantly different. In addition, such a concentration was non-toxic on NHDF cells, which were investigated by MTT assay. Therefore, formulation containing AgNPs at a concentration of 1280 µg/mL, chitosan 39 µg/mL and 50% v/v of WPU coating (Formula 8) will be further developed into commercial self-disinfection coatings.